The present invention relates to a magnetic recording medium such as a magnetic disk including a substrate. Information can be read out by a magnetic head from the surface of the medium. More specifically, the present invention relates to a magnetic record medium having an information recording density improved by minimizing the distance between the magnetic recording medium and the magnetic head.
The information recording density of magnetic disk devices has recently been increasing by as much as 60% every year. Effective approaches to increase the recording density include those intended to improve the characteristics of the magnetic recording medium or the head, the most effective one being to decrease the distance between the magnetic recording medium and the magnetic head while information is being read from or written on the medium.
When the magnetic recording medium is stopped, the head is held on a surface of the magnetic recording medium through contact with a region called a contact start stop (CSS)region. When a read/write instruction is provided to the magnetic disk unit, the disk unit rotates the recording medium and makes the head float above the recording medium. To reduce friction between the surface of the recording medium and the head, the surface of the substrate of the recording medium is embossed to provide favorable roughness, which is referred to as texture.
To fabricate the texture, if the recording medium has a low recording density, a method known as "scratch texture" is employed in which whetstone grain is used to scratch the substrate surface. As the demand for high-density recording medium increases, machining methods with higher precision are required. One such method is known as "laser texturing". This method uses laser light and can minimize the distance between the substrate and the magnetic head.
Conventionally, the laser texturing method has been primarily intended to form a texture in the CSS region but not in the data region, which serves as an information storage region in the recording medium. In this approach, the surface of the data region is made as flat as possible so that the distance between the substrate and the magnetic head is further reduced and a high recording density is achieved.
When the head is moved to a data region having no texture formed thereon, the flying characteristics of the head may be affected. This may result in the head colliding with the substrate in a seek operation, in which the head is moved to a desired position. Further, a protective film formed on the surface of the magnetic head or the recording medium may be damaged by the shock of the collision, which reduces the life of the magnetic disk device.
In addition, the head may collect lubricating agents, which are uniformly applied on the protective film. This lowers the friction characteristic of the magnetic head after the head is stopped in the CCS region. The lubricating agents that have been deposited on the head increase the static friction applied when the substrate starts to rotate. This leads to immobilization (sticktion) of the head on the substrate, and the substrate cannot be rotated.
The problem above is also influenced by the operational environment of the magnetic disk. Therefore, failure in the seek operation should be prevented so that the influence of the operational environment is eliminated as much as possible.
Accordingly, a method to fabricate the texture over the entire surface of the substrate has been proposed, which addresses the failure in seek operations. A method known as thin film texturing is used for a recording medium having a glass substrate in which fine projections are formed over its entire surface by a film of low melting point-metal surface by sputtering (Kogure, T., et al., "High-Coercivity magnetic Hard Disks Using Glass Substrates," J. Appl. Phys. 67(9):4701(1990).)
This method, however, requires the texture to be formed having a height and a density greater than certain values such that the frictional force between the substrate and the magnetic head is reduced in the CSS region, where the magnetic head alternately touches and leaves the substrate. This requirement limits the degree to which the distance between the substrate and the magnetic head can be reduced.
The present invention has been made in view of the problems associated with the prior art. Accordingly, an object of the present invention is to provide a recording medium in which the contact of the substrate with the magnetic head can be prevented in the seek operation while the distance between the substrate and the magnetic head is minimized.